Print apparatus utilise various techniques to disperse print agents such as coloring agent, for example comprising a dye or colorant, coating agents, thermal absorbing agents and the like. Such apparatus may comprise a printhead. An example printhead includes a set of nozzles and a mechanism for ejecting a selected agent as a fluid, for example a liquid, through a nozzle. In such examples, a drop detector may be used to detect whether drops are being ejected from individual nozzles of a printhead. For example, a drop detector may be used to determine whether any of the nozzles are clogged and would benefit from cleaning or whether individual nozzles have failed permanently.